This chapter focuses on psychometric considerations involved in the measurement of vocational interests. It discusses dimensions measured by vocational interest inventories. The chapter reviews broad factor taxonomies and also discusses why basic interests have been receiving more attention. The chapter also focuses on the kinds of stimuli and response formats that are used to collect vocational interest preference data. It presents some psychometric models that are used to scale and score various interest assessments and highlights some of the new research involving ideal point item response theory models. Occupational interests are located at the most specific end of the interest range and are often labeled using generic job names such as “nurse,” “reporter,” or “zookeeper.” In addition to the various kinds of interest dimensions, interest inventories sometimes measure dimensions from other individual difference domains to aid educational or vocational guidance. Some inventories measure perceived efficacy in performing certain tasks.